1. Field of the Invention
The present invention relates to isolation enclosures. In particular, the present invention relates to an isolation enclosure with ports that can be positioned in two dimensions, both horizontally and vertically.
2. Discussion of Background
Many industrial, medical and laboratory operations require relatively contamination-free, controlled environments. For example, solid state electronic components are frequently manufactured in "clean rooms" or "clean enclosures" where the concentration of particulates is kept to a minimum in order to ensure the quality of the products. Activities that require handling of hazardous materials are carried out in clean enclosures to protect the worker from the presence of harmful fumes or other contaminants; medical tests are frequently performed in clean enclosures to prevent contamination of samples.
For applications where it is necessary to protect workers from the contents of the enclosure, the interior of the enclosure is maintained at a pressure slightly below atmospheric pressure. Typically, fans exhaust the air passing through the enclosure to the atmosphere; in-line filters prevent toxic materials from entering the atmosphere. In the manufacture of pharmaceuticals and electronic components, it is necessary to protect the product from airborne contamination. For these applications, the interior pressure is somewhat greater than atmospheric pressure so that air tends to flow out of the enclosure.
Many different types of enclosures are available, known by as many names (including the terms "clean box," "hood," "clean work station," "containment," "glove box," "incubator," "material isolation enclosure," "clean enclosure," and "enclosure"). The most common type of enclosure is the familiar laboratory hood with an open front and an exhaust fan connected to the rear or top of the hood. The fan draws air into the hood from the open front, thus tending to sweep material away from the user. Enclosures with closed fronts generally include one or two access ports, sometimes having air-impermeable gloves sealed to the margin of the port to prevent external air from entering the enclosure. The user works on materials inside the box by placing his or her hands and arms in the gloves.
Many enclosures, including typical laboratory fume hoods, present two basic problems to the user. First, when the user stands or passes in front of the hood, an eddy current is formed by air being drawn past his body. This eddy current may draw toxic fumes towards him or out of the hood into the environment. While much research remains to be done on the causes and prevention of workplace-related illness and the effects of exposure to low levels of toxic compounds, it is clear that the incidence of employee illnesses and absenteeism are directly related to the quality of the work environment. An unhealthy work environment, with poor air quality due to the presence of contaminants, is associated with high rates of work-related illness and absenteeism.
Second, standard fume hoods draw a significant amount of air from the surrounding area (whether a manufacturing facility or a laboratory) and exhaust it. This warmed or cooled air must continually be replaced for the comfort and well-being of those who work in the area, forcing climate control systems to be operated at a higher capacity or for a higher percentage of the time, thereby resulting in higher utility costs. In some cases, existing climate control systems may fail to maintain adequate comfort levels for workers because of this waste of conditioned air.
In U.S. Pat. No. 5,205,624, Martell et al. describe an enclosure similar to a glovebox for isolating materials from the atmosphere, yet allowing the user to manipulate materials and apparatus located inside the enclosure. As represented schematically in FIG. 1, an enclosure 20 of this type is a box with structural framing members 22, 24, 26 surrounding a plurality of transparent plastic front panels 28 (three panels 28 are shown). In a conventional glovebox, the area below panels 28 (the "access zone") is open, so that the user may insert his or her hands into the box to manipulate materials and apparatus located therein.
In enclosure 20, however, the area below panels 28 defines an access zone 30 which contains an access frame 32 and two flexible, bellows-like curtains 34, 36. The user may insert his hands into the interior of enclosure 20 through an access space 38 defined by frame 32.
Frame 32 is movable to allow the user to access different portions of the interior of enclosure 30. As frame 32 is moved from side to side across access zone 30, curtains 34, 36 also move in such a way that the only opening into enclosure 20 is through the frame. In a preferred embodiment wherein a negative pressure is maintained inside enclosure 20, access frame 32 is made of members having an airfoil shape to reduce turbulence and enhance materials retention within the enclosure. Enclosure 20 gives the user access to most of its interior via frame 32, while reducing the needed airflow since the remaining portions of access zone 30 are curtained off.
Rune, et al. (U.S. Pat. No. 5,316,733) describe an isolation enclosure with two rubber gloves into which the user inserts his hands and forearms. The front of the enclosure includes two rigid plastic sheets: a first sheet with two oval openings and a second sheet, in front of the first sheet, with two circular openings to which the gloves are attached. The user pushes against the edges of the glove openings to slide the second sheet in the desired horizontal direction. Brendgord (U.S. Pat. No. 3,670,718) discloses a patient care wall having a window with a built-in upper-body suit that permits the user to perform work inside a sealed enclosure. Diccianni's ultra clean work station has two slidable access ports in an rectangular opening (U.S. Pat. No. 3,498,687). The ports are independently mounted, and each port has an iris-type closure. The remaining space in the opening is filled by collapsible panels.
Larger areas such as loading bays and warehouses may be isolated from the outside environment by means of door systems. By way of example, Weibull shows a loading bay door system having one or more movable frames with horizontally-foldable wall portions on either side (U.S. Pat. No. 4,104,836). Each frame supports a door consisting of accordion-fold panels. Lowe's system includes two doors, one of which opens upwardly across the full width of the doorway opening (U.S. Pat. No. 3,926,242). The other door consists of two outwardly-opening portions, one on each side of the doorway opening. These two doors can be adjusted to define a rectangular aperture of any desired height and width.
Many operations performed in an isolation enclosure require the user's hands to work at widely separated locations. For example, setting up or taking down equipment, or performing certain operations such as pipetting and column chromatography, may require one hand to be placed near the top of a piece of equipment and the other hand near the bottom. No known enclosure allows the user to have each hand at a different location inside the enclosure easily; typically, both hands must pass through one, relatively small opening. The size of this opening is subject to a severe tradeoff between arm mobility and airflow reduction, since the entire area not occupied by the user's arms is open to the outside. In particular, the vertical range of hand motion may be so restricted that work is essentially limited to two dimensions. Furthermore, for any given installation, only those persons whose elbows are approximately at the vertical level of the opening when standing or sitting are able to work comfortably; others, either taller or shorter, will quickly become fatigued.
There remains a need for a convenient, functional and ergonomically sound isolation enclosure. Such an enclosure would allow the operator easy access to substantially all the interior and to maintain an efficient, comfortable work position, while minimizing the transfer of air between the interior and the ambient atmosphere.